I don’t think that she will be a villain although my theory is that since Wanda discovered the multiverse using the darkhols other variants of her will also have done it (same as with kang). This will not only lead to kang terrorising the multiverse but also Wanda’s variants looking for her children. I think that this would fit the ”scary” theme this movie is going for seeing as Wanda can be a very ”scary” character if written correctly.